LONDON, Dec. 26 -- Ethiopian troops fought their way closer to the Somali capital of Mogadishu on Tuesday, pushing back militias loyal to the Islamic Courts movement that has until now controlled much of the country and has vowed to wage a guerrilla war against Ethiopia lasting "years and years and years."

Aid workers said the number of injured had surpassed 800, as thousands of civilians battered by drought, floods and now rockets and mortars continued to flee villages in droves.

U.N. officials warned of a humanitarian crisis in Somalia, while fears remained high that Ethiopia's aggressive military campaign could have disastrous consequences not only for Somalia but across the Horn of Africa.

"I find it perplexing what the Ethiopians are up to," said David Shinn, a former U.S. ambassador to Ethiopia. "Over the long term, I don't see where this gets them. And one wonders how long they can hang on in this situation, because eventually it's going to turn into a nasty guerrilla war, and I don't think the Ethiopians have the stomach to carry on with that kind of campaign."

It was unclear Tuesday whether Ethiopian troops were preparing to invade Mogadishu or merely surround it.

But Shinn and others noted that a force of 15,000 troops had failed to subdue the capital in 1993, when 18 U.S. troops were killed in an incident depicted in the book and film "Black Hawk Down."

At a news conference in Addis Ababa, Ethiopian Prime Minister Meles Zenawi said that he had no plans to push into Mogadishu but that the campaign was only half-completed. The only option now, he added, was to win.

He said that he was pleased at how swiftly the campaign had gone and that 3,000 to 4,000 Ethiopian troops had "broken the back" of the Islamic Courts movement, which he has repeatedly accused of supporting secessionist groups in Ethiopia.

As Ethiopian troops pushed ahead, however, the Islamic Courts militias appeared to withdraw almost simultaneously from their front line positions, suggesting a coordinated strategy rather than a chaotic retreat, analysts said.

It was unclear where the Islamic fighters went. Some were spotted with their battle gear around Mogadishu; analysts said it was likely that most headed into the bush to prepare for a war on their own terms.

"The Islamic Courts know they can't confront Ethiopian tanks and airplanes" with ground troops and trucks mounted with machine guns, Shinn said. "I think they'd love to suck Ethiopia deep into Somalia and then slowly try to pick them off as they get bogged down."

On Tuesday, Islamic Courts leader Sharif Ahmed again condemned the international community for failing to stop the Ethiopian attack, which is widely perceived to have U.S. support, and he said the war had "entered a new phase."

As the fighting continued, members of the U.N. Security Council called an emergency meeting in New York to discuss the conflict and consider a joint statement put forward by Qatar.

Ambassadors from the 15 countries on the council were briefed first by Secretary General Kofi Annan's special representative for Somalia, Francois Lonseny Fall, and then began debating the text of a statement calling for the withdrawal of Ethiopian forces from Somalia.

But U.S. diplomats said they would seek changes to the draft.

"We don't want to single out Ethiopia in that way and believe they have legitimate security concerns," a U.S diplomat said. "Our position is that we need all parties to return to dialogue."

The diplomat, who agreed to discuss aspects of the U.S. position in exchange for anonymity, said the United States would also push for a condemnation of the Islamic Courts' use of child soldiers in the conflict.

It was unclear whether the Security Council would be able to reach consensus on the statement before Wednesday. Meanwhile, a Somali envoy to Ethiopia said Ethiopian troops could take over Mogadishu in 24 to 48 hours.

State Department spokesman Gonzo Gallegos reiterated the U.S. position that Ethiopia "has genuine security concerns with regard to developments within Somalia and has provided support at the request of the legitimate governing authority."

President Bush spoke to Ugandan President Yoweri Museveni by telephone about the tension in the region, a White House spokesman said.

This month, faint hopes for a peaceful resolution to the conflict were pinned on a U.S.-sponsored U.N. resolution authorizing deployment of an African Union force, excluding Ethiopia and other neighboring states, to protect Somalia's interim government, which is in quasi-exile in the town of Baidoa, about 70 miles from Mogadishu.

The theory was that the force would remove Ethiopia from the volatile equation. But only Uganda has tentatively agreed to send troops to the African Union force, a commitment more recently in serious doubt. African Union officials have said any deployment could take months. And the Courts movement has said deployment of any such force would be considered an invasion.

Given those circumstances, some diplomats in the region have proposed the opposite of the African Union deployment: pushing for the complete withdrawal of all foreign forces.

A U.N. report this year found that at least 10 countries were in some way involved in the conflict in Somalia, a sign of the country's strategic importance in the region. And Monday, witnesses said fighters from Eritrea, a bitter foe of Ethiopia, as well as from Pakistan were among those fighting alongside the Islamic militias.

For his part, Ethiopia's Meles has described his own military intervention as self-defense.

Ethiopia and the United States have accused the Courts movement of harboring terrorists, a charge the organization has denied. Opposition groups in Ethiopia have said Meles, who supplies intelligence to the United States on Somalia, has exaggerated the terrorism claim to win U.S. support as his increasingly authoritarian government stands accused of human rights violations.

The United States and Ethiopia have been of one mind that a complete takeover of Somalia by the Islamic Courts is unacceptable, because of fears that the country could become a base for Muslim extremists.

Yet U.S. policy in Somalia has been widely criticized for having the opposite of its intended effect, often encouraging the expansion of the Courts movement.

This year, the United States supported warlords who called themselves an "anti-terrorism" coalition. The warlords generally bribed and terrorized ordinary Somalis, who came to despise them. The Islamic Courts came to power as an alternative to the hated warlords, establishing order based on Islamic law village by village and earning widespread support from beleaguered Somalis tired of 15 years of near-anarchy.

More recently, perceived U.S. support for Ethiopia, like U.S. sponsorship of the U.N. resolution calling for the African Union deployment, appears to have been used by the Courts movement to rally support.